Method of printing and coating paper



y 1951 D. B. BRADNER 2,555,266

METHOD OF PRINTING AND COATING PAPER Filed July 10, 1945 INVENTOR fi/ AATTORNEYS Patented May 29, 1951 METHOD OF PRINTING AND COATING PAPER Donald B. Bradner, Mount Healthy, Ohio, assignor to The Champion Paper and Fibre Company, Hamilton, Ohio, a corporation of Ohio Application July 10, 1945, Serial No. 604,166

This invention relates to a process of treating paper to provide in a single operation a printed, coated, cast-surfaced paper product suitable for use as labels, advertisin matter, packaging material, and for other purposes.

In the manufacture of high grade printed labels for cans, bottles or other containers, it is customary first to apply to paper stock a layer of aqueous coating of casein and mineral pigment. The freshly coated paper is then dried and supercalendered and ordinarily cut into sheets and sorted. Thereafter it is run through a printing press one or more times, and finally it is varnished or lacquered by the application of a solution of gums, resins or the like in alcohol which is driven off by heat.

In place of the varnishing operation, a transparent film of cellophane or the like is sometimes laminated over the printed job to enhance the appearance and to give added protection.

The principal object of the present invention is to provide a method which combines in one operation the processes of coating, printing, and waterproofing paper, cardboard, postcard and the like.

Another object is to provide a method of producing printed material of unusual brilliance, attractiveness and durability.

Another object is to provide a method of producing a relatively waterproof, highly glazed paper suitable as an ornamental packaging material.

Another object is to provide a method of making, in one operation, printed, coated paper having a cast surface "comparable in all respects with the highest grade cast surfaced paper which is printed and lacquered in separate operations by the best methods now employed.

A preferred method of carrying out the invention will first be described followed by examples of a number of modifications which have to date been found useful.

.19 Claims (Cl. 101--426) For carrying out the invention there is proinsolubilized into a state that prevents their bleeding upon contact with water and are simultaneously set or gelled to render them sufficiently rigid that they do not distort, skid or rumple up under the press roll in the succeeding operation. This chemical treatment also effects an ultimate substantial loosening of the bond holding the film to the casting surface.

The next operation consists in firmly pressing a web of paper, advantageously carrying a freshly applied' aqueous coating composition containing clay, calcium carbonate or other mineral pigment and an adhesive, against the printed treated film on the casting surface where it is allowed to dry. To facilitate the drying, the belt may be heated and a blast of hot air directed against the back of the paper. In this way the printed film is cemented firmly to the coated paper, and after drying the integrated product is detached from the casting surface.

In the accompanying drawing a single apparatus for carryin out the essential steps of the invention is diagrammatically illustrated. This apparatus forms no part of the present invention but a description thereof will assist in an understanding of the preferred procedure.

A polished metal belt I, which is advantageously of nickel, is carried on two large pulleys 2 and 3. Pulley 2 is driven in the direction of the arrow, by motor 5 through chain 6, speed reducer 1, chain 8, line shaft 10 and a gear transmission II.

The film-applying apparatus is shown at A. The film-forming composition is contained in pan l5 and is carried up by roll l6 and metered by an adjustable nip between rolls l6 and H, from which it is carried and spread by rolls l8 and I9, and is applied to the belt in a uniform layer by roll 20 at a point where the belt is backed up by a backing roll 2|. This train of film-applying rolls is driven from line shaft ID by a chain drive 22 and a known type of variable speed drive 24.

The printing devices are shown at B. This may be a conventional type of dry offset press which is here illustrated in a simple form as composed of ink fountain 30 with fountain roll 3|, and ductor roll 32 which transfers the ink to distributor rolls 33, 34, and 35 which apply the ink to the printing plate on plate cylinder 36. From this cylinder the image is transferred to the belt by transfer roll 3'1, the belt being backed up at this point by a backing roll 38. The press as a whole is driven from line shaft ill by chain 39 and variable speed drive 40 by which it may be accurately synchronized with the belt.

Devices for applying a chemical treatment to the ink and film are illustrated at C. A spray nozzle il is supplied with a suitable chemical solution (hereinafter more fully discussed) through a pipe 42-, andwith air under pressure through a pipe 23 so as to direct a spray of chemical onto the belt. One or more of the nozzles may be provided as required to distribute the chemical over the full width of the working surface of the belt. Any excess of the chemical solution may be blown from the belt by air supplied to nozzle as through pipe 45. Contamination of the air in the room may be prevented by a hood 35 from which the vapors are exhausted through a duct 41 by any suitable suction devices, not shown.

At D is shown apparatus for applying coating composition to the paper. A web of paper 59 is unwound from a supply roll i and passes over guide rolls 52 to a driven applicator roll 53 which dips into a pan 54 containing coating composition, which composition is carried up and applied in excess to paper web 59 by roll 53. The freshly coated web then passes around a rubber covered press roll 55 which presses it against belt I where it is supported on pulle 2 and thereby removes the excess coating from the paper. The excess coating flows back and drops into pan 54 for reuse. Coating composition is continuously circulated through pan 54 from a reservoir by conventional means, not illustrated in the drawing.

The drying system is illustrated at E. The upper run of the belt carries the paper, with its coating, printing, and film cemented thereto. In order to dry the paper and coating, means are provided-for supplying heat and carrying away the vapors. Heat is supplied below the belt by a heating medium such as hot air and steam supplied thereto in a box or conduit Bl, which may also contain steam heating coils or other heating devices. To carry away the vapors from the back of the drying paper, air may be supplied through a series of nozzles 62 supplied by a duct 63 connected to a suitable blower, not shown. The air as supplied may advantageously be heated to accelerate the drying.

The taking off of the dried paper from the belt and the winding of the finished paper is illustrated at F. The dried web is pulled from the belt I where it wraps around pulley 3 and led around guide rolls 65 and 66 to the winder 61 which may be driven from line shaft iii by a belt 68, which tends to keep the paper under tension and pull it from the belt as described.

In carrying out the invention the first step ordinarily consists in the application to the casting surface of a relatively thin layer of a filmforming composition. See A in the drawing. A variety of materials may be used for this purpose, some being better than others. A satisfactory film-forming composition should adhere sufiiciently tightly to the casting surface that it will not be separated therefrom in the printing operation. For most satisfactory printing results it is in general desirable to use inks of considerable tack, and this demands the use of a film material which will not pull loose from the casting surface. The rubber covering on the transfer roll also subjects the film to a considerable pull, which must be withstood.

I have also observed that in order to obtain a product having a surface most perfectly reproducing the finish of the casting surface, very 4 tight adherence of the film to the casting surface should be had.

On the other hand, the film must not be permanently adherent to the casting surface as otherwise it will not be detached cleanly with the paper when the paper reaches the take-off roll.

I have succeeded in accomplishing these diametrically opposed effects by using film-forming (compositions which are firmly bonded to the casting surface at the time of printing but which are rendered easily separable from the casting surface at the conclusion of the process by subjecting them to a desired chemical treatment, as will be more fully described below.

A still further requirement of the film is that it provide a suitable base to receive the ink in the printing operation without blurring or fiowing or otherwise distorting the image. For best results the film at the time of printing should be somewhat porous or absorptive to the ink. However, the film must not be so permeable as to allow the ink to penetrate entirely through the film and deposit on the casting surface, for fear of forming undesirable ghost images.

Compositions of rosin and casein dispersed with alkali in water are particularly useful filmforming compositions for the purpose of the present invention. By varying the proportions of casein and rosin and alkali used, the printing, waterproofing, adherence and other properties of the film may be varied over a considerable range. I prefer to use mixtures containing from 20 to per cent of either rosin or casein. One composition that has been found to be very satisfactory consists of a mixture of 60 parts of waterwhite rosin and 40 parts casein. The rosin is dissolved in caustic soda using 1244 parts NaOH per parts rosin, and the casein is dissolved in 29% ammonia water, using about 10 parts ammonia water per 100 parts casein. The mixture as applied to the casting surface contains 18-20% total solids, the solvent consisting of equal parts water and alcohol. Water alone may be used but the alcohol reduces the foaming tendencies, minimizes stipple and accelerates drying.

Shellac films deposited either in the form of aqueous compositions dispersed with ammonia or caustic soda, or as alcoholic solutions, have been found useful for the present purpose. Proteins, such as soybean protein and zein, and synthetic resins may be used as the film-forming compositions.

Only a very thin film i required0f the order of two pounds or less, dry Weight, per thousand square feet of surface. The film is advantageously applied to the casting surface by means of a roller mechanism as previously described, the amount applied being controlled in any well known manner.

A certain time is allowed to elapse between the application of the film-forming composition and the printing of the ink upon the film. During this interval the solvent used in the film-forming composition is allowed to evaporate more or less completely so that the film sets to a relatively rigid state and is firmly adherent to the casting surface.

Films thus produced provide an excellent printing base for the reception of deep colored inks, and the extreme flatness of the metal backing makes possible clean printing of fine halftones.

Although oil inks of the type commonly used in printing paper may be employed for printing One type of ink which has been found very satisfactory for the purpose consists of pigment, natural resins dispersed with alkali, a polyhydroxyl alcohol, and water. A typical example of such an ink is:

Parts Carbon black 100 Shellac 100 Sodium hydroxide Water 45 Diethylene glycol 68 Copal, manila, damar, or other natural resins can be used in place of shell-ac, the exact proportions of the ingredients being varied as desired.

Another type of ink which has given excellent results consists of pigment dispersed by a caseinrosin mixture in water ethylene glycol. In this type of ink the addition of sugar has been found desirable in improving the spreading and other properties of the ink. A typical ink is made as follows: 300 parts of water white rosin is heated with 276 parts of ethylene glycol with stirring. A solution containing 36 parts of sodium hydroxide and 30 parts of water is added to the above mixture of rosin and ethylene glycol while hot. Sixty parts of casein, 145 parts of water, and 7.2 parts of 33 /3% solution of caustic soda are heated until the casein is dissolved. To this solution is then added the solution of rosin and ethylene glycol and caustic soda. Thereafter 225 parts of sucrose is added and stirred in until it is dissolved. Four hundred and eighty parts of Dark Red pigment is then added and the whole mixture thoroughly ink milled to produce an ink having a total solids of 69.7 and a pH of 8.7. This formula consists of:

100 red pigment 12.5 casein 62.5 water white rosin 47.0 sucrose 57.4 ethylene glycol 37.5 water total 8.0 sodium hydroxide Inks suitable for the purpose may also include pigments or dyes dispersed in glue, gelatin or gum solutions, or in solutions of resinous materials in volatile solvents, or dyes capable of staining the film. The inks should have suitable spreading and working qualities for high quality printing, and they should not promote sticking to the belt by penetrating through the film and corroding or adhering to the belt or by preventing the necessary chemical reactions as by drying and forming an impenetrable barrier.

. Although only one printing press is shown in the drawing, the invention is not limited to the application of one color. Two or more presses may be used to give multi-color printing; and if desired, the printed ink may be dried by application of heat between printings. In this way, blurring or mixing of successive colors is prevented, nor are there the difficulties of register 6 due to dimensional changes of paper. Further more, the process is not limited to the above described dry offset method of printing; for example the ink may be imprinted directly on the film by means of a rubber printing plate instead of through the medium of a transfer roll.

The next step in the process is to subject the printed film on the casting surface to a chemical treatment to insolubilize and gel the film and/or the ink so that neither will bleed or redisperse in water but will assume a sufficiently firm or rigid condition that there will be no blurring, flowing or distortion under the pressure roll of the succeeding operation. For this purpose I prefer to apply a fairly heavy spray of an aqueous solution of a heavy metal or an acid. For example, a solution containing 50 grams of magnesium sulfate per liter was sprayed on a rosin-casein film carrying a rosin, casein, ethylene glycol, pigment ink. An excess of liquid was sprayed'upon the printed film, which was then subjected to a blast of air to remove the excess. The ink and the film were thereby gelled or insolubilized and set to a relatively firm consistency so that when the paper web carrying a fluid aqueous coating composition was pressed against it there was no bleeding or blurring of even the fine halftone in the printing. Presumably alkali rosinate and alkali caseinate comprising the film and the ink were converted into insoluble magnesium salts. Besides, the film was rendered substantially waterproofthat is, the film on the finished paper product would not disintegrate or redisperse when a drop of water was rubbed back and forth under the finger. Finally the integrated paper is detached from the casting surface without damage due to adherence. Carrying out the film-forming, printing and paper-cementing operations exactly as described but omitting the application of the spray gave a product in which the halftones were blurred, a very ugly pattern was formed all over the printing, and the unprinted parts of the film appeared smeared and mottled. Besides, the gloss or finish was lower.

In case an oil ink is used in the printing step it is usually advisable to introduce the insolubilizing step ahead of the printing operation, as otherwise the chemical treatment may not penetrate the ink to affect the underlying film.

In place of magnesium sulfate, other compounds may be used such as for example calcium chloride, zinc sulfate, aluminum sulfate, acetic acid, hydrochloric acid, sodium bisulfate, etc,

The useful effects produced by insolubilizing the ink and especially the film are more than a mere waterproofing action. The action is accompanied by a significant decrease in the adherence of the finished integrated paper to the casting surface in a manner not clearly understood. Consequently the method permits the application of films which before the insolubilizing step are very tightly bound to the casting surface and thereby more perfectly assume the finish of the casting surface. The insolubilizing step apparently in no way disturbs this appearance of the film.

The next step in the operation is the incorporation of the printed film with the paper. Advantageously a layer of coating composition containing an aqueous dispersion of mineral pigment (clay, calcium carbonate, etc.) and adhesive (casein, soybean protein, starch, etc.) is applied to the paper to enhance the appearance of the finished paper and to facilitate the strip ping operation. This coating material may be applied in any well known manner, as by the roller mechanism shown at D in the drawing, and while it is still in a formable condition it is pressed against the printed film on the casting surface. Alternatively a part of or all the coat ing may be applied to the film layer before application to the paper. In any case the coating, due to its adhesive ingredient, becomes well bonded to the paper base during the subsequent drying operation on the belt and also the printed film becomes firmly cemented to the coated paper. When the drying is completed the integrated product consisting of paper, coating, printing and film, separates cleanly from the belt or other casting surface and may be wound into a roll or cut into sheets as desired. 7

The finished product is a printed paper having a surface that substantially duplicates the finish of the casting surface, a brilliance of ink with- 1:

out bronziness, unusual brightness and purity of color, and is substantially free from water spotting or finger marking. Labels and other printed matter prepared by this process are greatly superior in appearance to products made by printing and varnishing on the best grades of coated paper.

Although the invention is for most purposes carried out by first laying down a film and then printing on the film prior to cementing to the paper, under some circumstances the use of either the film or the printing may be dispensed with. Thus, in case it is desired to make a fancy wrapping or box liner, the printing step may be omitted. In this case the film may be applied as described and thereafter waterproofed or otherwise chemically treated while in contact with the casting surface, before the freshly coated paper is pressed in contact with it.

In some cases it may be desirable to print difilm-forming composition across the entire surface of the casting surface but to leave portions thereof bare to facilitate pasting or a subsequent printing on the finished product at these unfilmed spaces, as is commonly done in the varnish label art.

Other variations of the method may be employed without departing from the scope of the invention. Thus the application of the insolubilizing agent need not be eifected by a spray device. and ink may be passed into a suitable bath of the chemical and the excess removed in any suitable manner as by blowing off. Or the liquid may be applied by a roller mechanism, the surface of which is slightly spaced apart from the belt surface.

In some cases, particularly where no ink is applied to the film, or where the ink is of such a nature not to squash or spread under the press roll, the reacting chemical may be incorporated directly in the coating applied to the paper. For example an aqueous coating containing starch, pigment and a little calcium chloride may be applied to the paper and pressed against a rosincasein film on the casting surface.

Also it is not necessary to employ a mineral coating on the paper of the type described. If desired, a non-aqueous coating such as for example a layer of adhesive in organic solvent,

For example, the belt carrying the film I may be used to cement the ink and/or film to the paper. Or an adhesive-containing layer may be applied to the belt over the insolubilized film and/or ink, and plain paper thereafter pressed against the belt to effect the required cementation.

I claim:

l. In a process of the class described comprising applying coating composition upon a casting surface and cementing paper to the applied coating while on the casting surface, the step which comprises, prior to the cementing of the paper to the coating, chemically reacting the coating with an agent to insolubilize it and-set it to a 4. relatively firm physical condition before detach- 2. In a process of the class described comprising applying coating composition upon a casting surface, applying a second coating composition to a travelling web of paper, pressing the wet coated side of the paper against the coating on the casting surface, and after drying removing the paper and both coatings from the casting surface as an integrated cast surfaced product, the step which comprises subjecting the first coating while on the casting surface, to the action of an agent to water insolubilize it and set it to a relatively firm physical condition before detaching. V

3. A' process of the class described which comprises applying coating composition to a travelling casting surface, treating the coating on the casting surface with an agent to render it non dispersible in water and sufficiently rigid to minimize distortion in the subsequent pressing step, applying an aqueous coating containing mineral pigment to a travelling web of paper, pressing the Wet coated paper against the coating on the casting surface, drying the paper and separating the composite paper and coatings from the casting surface.

4. A process of the class described which comprises applying a substantially continuous layer of film-forming coating composition to a casting surface, subjecting the applied coating composition to the chemical action'of an agent to prevent its subsequent dispersion on contact with Water, cementing paper to the chemically treated coating and detaching the paper with the coating from the casting surface after the coating has assumed a cast surface condition.

5. Process of claim 4 wherein the film-forming composition comprises a water miscible composition containing a rosin soap.

6. Process of claim 4 wherein the film-forming composition contains rosin and casein.

'7. A process of the class described which comprises applying a substantially continuous layer of film-forming coating composition to a casting surface, printing an ink upon said layer, sub- ,jecting the ink and coating to a chemical treatment to prevent subsequent dispersion thereof on contact with water, cementing paper to the printed film layer and detaching the-paper carrying the printed film layer from the casting 'surface after the film layer has assumed a cast condition.

8. Process of claim 7 wherein the ink is miscible with water.

9. A process of the class described which comprises applying a substantially continuous layer of film-forming composition to a casting surface, partially drying the said layer, printing upon the exposed surface of said layer, applying a solution to vinsolubilize the printed layer, and render it sufficiently firm to minimize distortion in the subsequent pressing step, pressing a freshly coated web of paper against the printed layer, drying the resulting product and detaching the coated paper carrying the printed layer from the casting surface after the layer has been hardened to a cast surface condition.

10. A process of the class described which comprises applying a substantially continuous layer of film-forming composition to a casting surface, partially drying the said layer, printing upon the exposed surface of said layer with an ink containing a substantial percentage of water, applying a chemical agent to render the printed layer substantially non-dispersible in water, cementing paper carrying an aqueous coating to said printed layer and detaching the paper carrying the printed layer from the casting surface after the said layer has been hardened to a cast surface condition.

11. A process of the class described which comprises printing a water miscible ink upon a-casting surface, contacting the printing with an agent to gel the ink and render it substantially non-dispersible in water, cementing the treated printing to paper carrying an aqueous dispersion comprising adhesive and mineral pigment, and detaching the printed coated paper from the casting surface after it has dried in contact therewith.

12. A process of the class described which comprises applying aqueous coating composition con-- taining an ingredient precipitatable with a heavy metal salt, to a travelling casting surface, contacting'the applied coating with an aqueous solution of a heavy metal salt, cementing paper to the coating on the casting surface and detaching paper and coating from the casting surface after the coating has assumed a cast surface condition.

13. A process of the class described which comprises applying to a moving casting surface a layer of film-forming composition comprising casein and rosin dispersed in aqueous alkaline medium, evaporating water therefrom to form a film suitable for the acceptance of ink, transferring to the film a printed image by dry offset, said image comprising an ink containing rosin dispersed in a water-miscible medium, spraying the exposed surface of the printed film with an aqueous solution capable of gelling the rosin whereby the film and ink are prevented from redispersing in contact with water, applying aqueous coating composition comprising mineral pigment and adhesive to a web of paper, pressing the coated paper against the printed film on the casting surface, drying the coating and hardening the film while the film is in contact with the casting surface and detaching therefrom the paper, coating, printing, and film as an integral product.

14. A process of the class described which com prises forming on a moving metallic casting surface a tightly adherent film, printing on said film with a water compatible ink, contacting said printed film with an aqueous solution to insolubilize said printed film and reduce the adherence of said film to the casting surface, cementing a web of paper carrying aqueous coating composition to the printed film and detaching the paper, carrying the coating, printing, and film, from the casting surface after the coating has dried and the film has assumed a cast surface.

15. Process of claim 14 wherein the film is prepared from an alkaline dispersion containing rosin.

16. A process of the class described which comprises applying an aqueous dispersion of filmforming composition having a pH in excess of '7 to a casting surface, partially'drying the applied composition to form a tightly adherent film, printing on said film with a tacky, aqueous dispersible ink, acidifying said printed film to give a pH less than 7 whereby the film is rendered less adherent to the casting surface, pressing a web of papercarrying a fluid aqueous coating against said printed treated film, drying the composite paper while in contact with the casting surface and detaching therefrom the resulting cast surfaced printed coated paper.

17. A process of the class described which comprises'applying a layer of aqueous film-forming composition on a polished metal casting surface, evaporating solvent from said applied layer until a tightly adherent film is produced, printing thereon a tacky ink comprising pigment and resin dispersed in a water miscible liquid, applying aqueous solution of a precipitating agent to the printed film whereby the ink and film are rendered substantially non-dispersible in water and relatively non-distortable, removing excess precipitating agent, pressing paper carrying a fiuid aqueous coating composition against the treated printed film and drying the product while carried by the casting surface to produce a highly finished cast surfaced coated, printed filmed paper when detached from the casting surface.

18. A process of the class described which comprises applying to a metal casting surface an aqueous composition containing rosin and casein dispersed by an alkaline compound, evaporating water from said applied composition to form a printing base, printing thereon a composition comprising pigment, adhesive, and a mixture of water and polyhydric alcohol, applying aqueous solution of a heavy metal salt to set the compositions on the casting surface to a state where they will not distort or bleed when subjected to the hereinafter mentioned pressing action, pressing a paper base carrying on its contacting surface a fluent aqueous coating composition comprising mineral pigment and adhesive against the treated compositions on the casting surface,

evaporating water through the back of the paper by heat while the paper is cemented by the casting surface, and detaching the dried composite paper from the casting surface.

19. A process of the class described which comprises applyirig to a metal casting surface an aqueous composition containing rosin and casein dispersed by an alkaline compound, evaporating water from said applied composition to form a printing base, printing thereon a composition comprising pigment, adhesive, and a mixture of water and polyhydric alcohol, applying a dilute acid solution to set the compositions on the casting surface to a state where they will not distort or bleed when subjected to the hereinafter mentioned pressing action, pressing a paper base carrying on its contacting surface a fluent aqueous coating composition comprising mineral pigment and adhesive against the treated compositions on the casting surface, evaporating water through the back of the paper by heat while the paper is cemented by the casting surface, and detaching the dried composite paper from the casting surface.

DONALD B. BRADNER.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Hart May 3, 1881 Mandel Oct. 28, 1890 Harbeck Jan. '12, 1909 Weinheim July 26, 1910 Gurwick May 21, 1929 Bryan Aug. 11, 1931 Massey Aug. 8, 1933 Van Wirt Mar. 6, 1934 Number 12 Name Date Montgomery et a1. Jan. 28, 1936 Murray Apr. 28, 1936 Hooft Mar. 1, 1938 Reynolds Aug. 15, 1939 Fischer et a1 June 25, 1940 Grupe June 30, 1942 Francis et a1. July 18, 1944 Ortolano Jan. 30, 1945 OTHER REFERENCES Corp., 330 West 42nd 817., N. Y. (1940).

(Copy in Div. 17, pp. 400.) 

7. A PROCESS OF THE CLASS DESCRIBED WHICH COMPRISES APPLYING A SUBSTANTIALLY CONTINUOUS LAYER OF FILM-FORMING COATING COMPOSITION TO A CASTING SURFACE, PRINTING AN INK UPON SAID LAYER, SUBJECTING THE INK AND COATING TO A CHEMICAL TREATMENT TO PREVENT SUBSEQUENT DISPERSION THEREOF ON CONTACT WITH WATER, CEMENTING PAPER TO THE PRINTED FILM LAYER AND DETACHING THE PAPER CARRYING THE PRINTED FILM LAYER FROM THE CASTING SURFACE AFTER THE FILM LAYER HAS ASSUMED A CAST CONDITION. 